This application is based on Japanese Patent Application Nos. 2001-308925, 2001-206471 and 2002-145513 filed Oct. 4, 2001, Jul. 6, 2001 and May 20, 2002, respectively, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a planetary gear type multiple-step transmission interposed between a drive power source and drive wheels of a vehicle such as an automobile and a railcar.
2. Discussion of Related Art
For vehicles, there are widely used planetary gear type multiple-step transmissions which have a plurality of predetermined speed ratios or operating positions (gear positions) that are selectively established. Such planetary gear type multiple-step transmissions are desired to be not only simple in construction and small in size and to provide a large number of operating positions and a wide range of speed ratio, but also to provide speed ratios that change as geometric series or nearly geometric series.
There has been proposed a planetary gear type multiple-step transmission which has seven operating positions. Representative examples of this kind of planetary gear type multiple-step transmission include a transmission of a third embodiment of FIGS. 5 and 6 and a transmission of a fourth embodiment of FIGS. 7 and 8 of JP-A-2000-266138. Although these transmissions provide a relatively large number of operating positions and a relatively wide range of speed ratio, the transmissions have a large overall length due to the use of four planetary gear sets, and undesirably suffer from a relatively low degree of freedom in its installation on a vehicle.
It is therefore an object of the present invention to provide a small-sized planetary gear type multiple-step transmission which has a relatively large number of operating positions and a relatively wide range of speed ratio.
The above object may be achieved according to a first aspect of this invention, which provides a planetary gear type multiple-step transmission for a vehicle, having seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed, a second-speed, a third-speed, a fourth-speed, a fifth-speed, a sixth-speed and a seventh-speed position, the transmission comprising an input rotary member, an output rotary member, a first, a second and a third planetary gear set each including a sun gear, a carrier and a ring gear, and further comprising a first, a second and a third brake, and a first, a second, a third and a fourth clutch, wherein an improvement comprises:
(a) a first, a second, a third, a fourth and a fifth rotary element each of which is constituted by at least one of the sun gears, carriers and ring gears of the first, second and third planetary gear sets, and rotating speeds of the first, second, third, fourth and fifth rotary elements being represented by respective parallel straight lines of a collinear chart, which lines are arranged in a direction from one of opposite ends of the collinear chart toward the other end, the first rotary element being selectively brought to a stationary state by the first brake, and the second rotary element being selectively brought to a stationary state by the second brake, while the third rotary element being selectively brought to a stationary state by the third brake, the fifth, third and first rotary elements being selectively connected to the input rotary member by the first, second and third clutches, respectively, and the third rotary element being selectively connected to the input rotary member through the second clutch, and the third rotary element rotary element being selectively brought to a disconnected state by the fourth clutch, while the fourth rotary element being connected to the output rotary member; and
(b) the first-speed position being established by engaging the first clutch and the third brake, or the first and fourth clutches and the third brake, and the second-speed position being established by first clutch and the second brake, while the third-speed position being established by engaging the first and fourth clutches and the first brake, the fourth-speed position being established by engaging the first and second clutches and the first brake, the fifth-speed positioning being established by engaging the first, second and fourth clutches, the sixth-speed position being established by engaging the second and fourth clutches and the first brake, the seventh-speed position being established by engaging the second and fourth clutches and the second brake.
In a first preferred form of the transmission according to the first aspect of this invention, each of the first, second and third planetary gear sets is a single-pinion type planetary gear set, and the first rotary element consists of the sun gear of the first planetary gear set, and the second rotary element consists of the carrier of the first planetary gear set and the ring gear of the second planetary gear set, while the third rotary element consists of the ring gear of the first planetary set, the carrier of the second planetary gear set and the ring gear of the third planetary gear set, the fourth rotary element consisting of the carrier of the third planetary gear set, and the fifth rotary element consisting of the sun gear and the of the second planetary gear set and the sun gear of the third planetary gear set.
In a second preferred form of the transmission according to the first aspect of the invention, the first planetary gear set is a double-pinion type planetary gear set, while each of the second and third planetary gear sets is a single-pinion type planetary gear set, and the first rotary element consists of the sun gear of the first planetary gear set, and the second rotary element consists of the ring gear of the first planetary gear set and the ring gear of the second planetary gear set, while the third rotary element consists of the carrier of the first planetary set, the carrier of the second planetary gear set and the ring gear of the third planetary gear set, the fourth rotary element consisting of the carrier of the third planetary gear set, and the fifth rotary element consisting of the sun gear and the of the second planetary gear set and the sun gear of the third planetary gear set.
In a third preferred form of the transmission according to the first aspect of this invention, the first planetary gear set is a double-pinion type planetary gear set, while each of the second and third planetary gear sets is a single-pinion type planetary gear set, and the first rotary element consists of the carrier of the first planetary gear set, and the second rotary element consists of the ring gear of the first planetary gear set and the ring gear of the second planetary gear set, while the third rotary element consists of the sun gear of the first planetary set, the carrier of the second planetary gear set and the ring gear of the third planetary gear set, the fourth rotary element consisting of the carrier of the third planetary gear set, and the fifth rotary element consisting of the sun gear and the of the second planetary gear set and the sun gear of the third planetary gear set.
In the planetary gear type multiple-step transmission according to the first aspect of the present invention described above, the first, second and third planetary gear sets are arranged to provide providing a sufficiently wide range of speed ratio, thereby permitting not only high-speed running of the vehicle, but also stable starting of the vehicle on an uphill road, without an increase of the required size of the transmission.
In one advantageous arrangement of the first, second and third preferred forms of the first aspect of the invention described above, the transmission further has a rear drive position for driving the vehicle in a reverse direction, the rear drive position being established by engaging the third and fourth clutches and the third brake, the first, second and third planetary gear sets having respective gear ratios which are determined such that the rear drive position has a speed ratio between those of the first-speed and second-speed positions. In this arrangement, the rear drive position having a speed ratio which is lower than that of the first-speed position and higher than that of the second-speed position can be established by engaging actions of the third and fourth clutches and the third brake.
In another advantageous arrangement of the second and third preferred form of the first aspect of the invention described above, the transmission further has a rear drive position for driving the vehicle in a reverse direction, the rear drive position being established by engaging the second clutch and the first and third brakes, and the first, second and third planetary gear sets have respective gear ratios which are determined such that the rear drive position has a speed ratio between those of the first-speed and second-speed positions. In this arrangement, the rear drive position having a speed ratio which is lower than that of the first-speed position and higher than that of the second-speed position can be established by engaging actions of the second clutch and the first and third brakes.
In a further advantageous arrangement of the second and third preferred forms of the first aspect of the invention described above, the transmission further has a rear drive position for driving the vehicle in a reverse direction, the rear drive position being established by engaging the third clutch and the first and third brakes, and the first, second and third planetary gear sets have respective gear ratios which are determined such that the rear drive position has a speed ratio between those of the first-speed and second-speed positions. In this arrangement, the rear drive position having a speed ratio which is lower than that of the first-speed position and higher than that of the second-speed position can be established by engaging actions of the third clutch and the first and third brakes.
In a further preferred form of the transmission according to the first aspect of the invention, the first, second and third planetary gear sets are arranged between the input and output shafts. According to this form of the invention, the transmission can be made small-sized, yet permitting not only high-speed running of the vehicle, but also stable starting of the vehicle on an uphill road.
In a still further preferred form of the transmission according to the first aspect of the invention, an output of an engine of the vehicle is transmitted to the input shaft through a torque converter. This form of the invention provides a compact automatic transmission.
In a yet further preferred form of the first aspect of the invention described above, the transmission further comprises a one-way clutch disposed in parallel with one of the first, second, third and fourth clutches and the first, second and third brakes. This form of the invention permits easier control of shifting actions of the transmission. For instance, the one-way clutch is disposed in parallel with the third brake disposed between the third ring gear and the stationary rotary member. In this instance, the first-speed position is established by engaging the third brake, such that an engine brake application to the vehicle in this first-speed position is inhibited if the one-way clutch is engaged.
The object indicated above may also be achieved according to a second aspect of the present invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, a third and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the first carrier and the second ring gear being connected to each other;
the first ring gear and the second carrier being connected to each other through the fourth clutch;
the second carrier and the third ring gear being connected to each other while the second and third sun gears being connected to each other;
the input rotary member being connected to the first sun gear through the third clutch;
the input rotary member being connected to the first ring gear through the second clutch;
the input rotary member being connected to the second and third sun gears through the first clutch;
the first brake being disposed between the stationary rotary member and the first sun gear;
the second brake being disposed between the stationary rotary member and the first carrier;
the third brake being disposed between the third ring gear and the stationary rotary member; and
the output rotary member is connected to the third carrier.
In one preferred form of the second aspect of the invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first carrier and the stationary rotary member to each other,
the third-speed position being established by engaging the first clutch and the first brake to connect the input rotary member to the second and third sun gears, and to connect the first sun gear and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and second clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first ring gear, and to connect the first sun gear and the stationary rotary member,
the fifth-speed position being established by engaging the first, second and fourth clutches to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first ring gear, and to connect the first ring gear and the second carrier.
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the first ring gear, to connect the first ring gear and the second carrier to each other, and to connect the first sun gear and the stationary rotary member, and
the seventh-speed position beings established by engaging the second and fourth clutches and the second brake to connect the input rotary member to the first ring gear, to connect the first ring gear and the second carrier, and to connect the second carrier and the stationary rotary member to each other.
The object indicated above may also be achieved according to a third aspect of this invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, a third and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the first and second carriers and the third ring gear being connected to each other;
the first and second ring gears being connected to each other;
the second and third sun gears being connected to each other;
the input rotary member being connected to the second and third sun gears through the first clutch:
the input rotary member being connected to the first carrier, or to an assembly of the first and second carriers and the third ring gear, through the second clutch;
the input rotary member being connected to the first sun gear through the third clutch;
the fourth clutch being disposed between the first and second carriers;
the first brake being disposed between the first sun gear and the stationary rotary member;
the second brake being disposed between the stationary rotary member and an assembly of the first and second ring gears;
the third brake being disposed between the stationary rotary member and an assembly of the first and second carriers and the third ring gear; and
the third carrier being connected to the output rotary member.
In one preferred form of the third aspect of this invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first and second ring gears to the stationary rotary member to each other,
the third-speed position being established by engaging the first and fourth clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and second clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first or second carrier, and to connect the first sun gear and the stationary rotary member to each other,
the fifth-speed position being established by engaging the first, second and fourth clutches to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first or second carrier, and to connect the first and second carriers to each other,
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the first or second carrier, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member, and
the seventh-speed position being established by engaging the second and fourth clutches and the second brake to connect the input rotary member to the first or second carrier, to connect the first and second carriers to each other, and to connect the first and second ring gear to the stationary rotary member to each other.
The object indicated above may also be achieved according to a fourth aspect of the present invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the second carrier and the third ring gear being connected to each other;
the first and second ring gears being connected to each other;
the second and third sun gears being connected to each other;
the input rotary member being connected to the second and third sun gears through the first clutch;
the input rotary member being connected to the first carrier through the second clutch;
the fourth clutch being disposed between the first and second carriers;
the first brake being disposed between the first sun gear and the stationary rotary member;
the second brake being disposed between the first and second ring gears;
the third brake being disposed between the second carrier and the third ring gear; and
the third carrier being connected to the output rotary member.
In one preferred form of the fourth aspect of the invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first and second ring gears to the stationary rotary member to each other,
the third-speed position being established by engaging the first and fourth clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and second clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first carrier, and to connect the first sun gear and the stationary rotary member to each other,
the fifth-speed position being established by engaging the first, second and fourth clutches to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first carrier, and to connect the first and second carriers to each other,
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the first carrier, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member, and
the seventh-speed position being established by engaging the second and fourth clutches and the second brake to connect the input rotary member to the first carrier, to connect the first and second carriers to each other, and to connect the first and second ring gear to the stationary rotary member to each other.
The object indicated above may also be achieved according to a fifth aspect of this invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, a third and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the second carrier and the third ring gear being connected to each other;
the first and second ring gears are connected to each other; the second and third sun gears being connected to each other;
the input rotary member being connected to the second and third sun gears through the first clutch;
the input rotary member being connected to the second carrier and the third ring gear through the second clutch;
the input rotary member being connected to the first carrier through the third clutch;
the fourth clutch being disposed between the first and second carriers;
the first brake being disposed between the first sun gear and the stationary rotary member;
the second brake being disposed between the first and second ring gears;
the third brake being disposed between the second carrier and the third ring gear; and
the third carrier being connected to the output rotary member.
In one preferred form of the fifth aspect of the invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first and second ring gears to the stationary rotary member to each other,
the third-speed position being established by engaging the first and fourth clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and third clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first carrier, and to connect the first sun gear and the stationary rotary member to each other,
the fifth-speed position being established by engaging the first and second clutches to connect the input rotary member to the second and third sun gears and to connect the input rotary member to the second carrier,
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the second carrier, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member, and
the seventh-speed position being established by engaging the second clutch and the second brake to connect the input rotary member to the second carrier, to connect the first and second ring gears to the stationary rotary member to each other.
The object indicated above may also be achieved according to a sixth aspect of this invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the second carrier and the third ring gear being connected to each other;
the first and second ring gears being connected to each other;
the second and third sun gears being connected to each other;
the input rotary member being connected to the second and third sun gears through the first clutch;
the input rotary member being connected to the first sun gear through the second clutch;
the fourth clutch being disposed between the first sun gear and the second carrier;
the first brake being disposed between the first carrier and the stationary rotary member;
the second brake being disposed between the first and second ring gears;
the third brake being disposed between the second carrier and the third ring gear; and
the third carrier being connected to the output rotary member.
In one preferred form of the sixth aspect of the invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first and second ring gears to the stationary rotary member to each other,
the third-speed position being established by engaging the first and fourth clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the first and second carriers to each other, and to connect the first sun gear and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and second clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first carrier, and to connect the first carrier and the stationary rotary member to each other,
the fifth-speed position being established by engaging the first, second and fourth clutches to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first sun gear, and to connect the first sun gear and the second carrier,
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the first sun gear, to connect the first sun gear and the second carrier to each other, and to connect the first carrier and the stationary rotary member to each other, and
the seventh-speed position being established by engaging the second and fourth clutches and the second brake to connect the input rotary member to the first sun gear, to connect the first sun gear and the second carrier to each other, and to connect the first and second ring gears to the stationary rotary member.
The object indicated above may also be achieved according to a seventh aspect of the present invention, which provides a planetary gear type multiple-step transmission for a vehicle, comprising a stationary rotary member, an input rotary member, an output rotary member, a first, a second and a third planetary gear set which are disposed coaxially with each other, a first, a second, a third and a fourth clutch, and a first, a second and a third brake, and wherein the first planetary gear set including a first sun gear, a first planetary gear, a first carrier rotatably supporting the first planetary gear, and a first ring gear meshing with the first sun gear through the first planetary gear, the second planetary gear set including a second sun gear, a second planetary gear, a second carrier rotatably supporting the second planetary gear, and a second ring gear meshing with the second sun gear through the second planetary gear, the third planetary gear set including a third sun gear, a third planetary gear, a third carrier rotatably supporting the third planetary gear, and a third ring gear meshing with the third sun gear through the third planetary gear, the transmission being operable to transmit a rotary motion of the input rotary member to the output rotary member such that a ratio of the speed of the input rotary member to the speed of the output rotary member is variable in steps, wherein an improvement comprises:
the second carrier and the third ring gear being connected to each other;
the first and second ring gears being connected to each other;
the second and third sun gears being connected to each other;
the input rotary member being connected to the second and third sun gears through the first clutch;
the input rotary member being connected to the second carrier and the third ring gear through the second clutch;
the input rotary member being connected to the first sun gear through the third clutch;
the fourth clutch being disposed between the first sun gear and the second carrier;
the first brake being disposed between the first carrier and the stationary rotary member;
the second brake being disposed between the first and second ring gears;
the third brake being disposed between the second carrier and the third ring gear; and
the third carrier being connected to the output rotary member.
In one preferred form of the seventh aspect of the invention described above, the transmission has seven forward drive positions for driving the vehicle in a forward direction, the seven forward drive positions including a first-speed position having a highest speed ration, a second-speed position having a speed ratio lower than that of the first-speed position, a third-speed position having a speed ratio lower than that of the second-speed position, a fourth-speed position having a speed ratio lower than that of the third-speed position, a fifth-speed position having a speed ratio lower than that of the fourth-speed position, a sixth-speed position having a speed ration lower than that of the fifth-speed position, and a seventh-speed position having a speed ratio lower than that of the sixth-speed ratio,
and wherein the first-speed position is established by engaging the first clutch and the third brake to connect the input rotary member to the second and third sun gears, and to connect the third ring gear and the stationary rotary member to each other,
the second-speed position being established by engaging the first clutch and the second brake to connect the input rotary member to the second and third sun gears, and to connect the first and second ring gears to the stationary rotary member to each other,
the third-speed position being established by engaging the first and fourth clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the first sun gear and the second carrier to each other, and to connect the first carrier and the stationary rotary member to each other,
the fourth-speed position being established by engaging the first and third clutches and the first brake to connect the input rotary member to the second and third sun gears, to connect the input rotary member to the first sun gear, and to connect the first carrier and the stationary rotary member to each other,
the fifth-speed position being established by engaging the first and second clutches to connect the input rotary member to the second and third sun gears, and to connect the input rotary member and the second carrier to each other,
the sixth-speed position being established by engaging the second and fourth clutches and the first brake to connect the input rotary member to the second carrier, to connect the first sun gear and the second carrier to each other, and to connect the first carrier and the stationary rotary member to each other, and
the seventh-speed position being established by engaging the second clutch and the second brake to connect the input rotary member to the second carrier, and to connect the first and second ring gears to the stationary rotary member.